I think you are discounting the level of headache the N. African route can be for Japan. If America goes N. Africa s/he can be sending in 12 grounds units a round to Persia quickly, plus fighters. That’s as good an anchor as can be, and suddenly, Japan finds him/herself defending Industrial complexes in India and FIC against a possible American invasion, while America is free to calculate his or her least chance to kill all attackers and move the rest of his or her forces to the German front as reinforcements. (If America wants an 80% chance to win, then they calculate that. If they want 99% then that. If they only want 33% they can send more forces to Germany.)
Persia is not THAT far from Algeria. Especially for tanks. And if you play NAs and America gets Mechanized Infnatry, just forget going the southern route at all because you’ll never make it.
(E. Can/E. USA –> Algeria --> Libya --> Egypt --> T-J --> Persia = 5 Turns max. Japan needs twice as many rounds to be a reasonable threat to Moscow, let alone hold Persia.)
And no, for the record, Germany CANNOT defend N. Africa against British forces and Americans. (I like using Britian to take Algeria and Libya. Softens the blow of Japanese acquisitions a little, especially if England also took Norway.) Sorry, but there’s no way 1 transport can move enough troops to N. Africa to even threaten the Allies.